As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CRUISE FLIGHT AT FL 260 CABIN STARTED TO CLIMBING AT 500’ PER MIN. ATC WHICH CLEARED THE CREW TO 12000’. DURING THE DECENT CABIN INCREASED ABOVE 12500 CAUSING PASSENGER MASK TO DEPLOY. DIVERTED TO KSMF. LANDING WAS UNEVENTFUL. MAINTENANCE REPLACED THE LEFT AND RIGHT BLEED AIR FLOW CONTROL VALVES. OPERATIONAL CHECK FLIGHT PENDING.